Animal shelters were chosen based on distinct precipitatio

1
The Effects of Precipitation Zones on the
Occurrence of Parasitism in Dogs at Different
Locations in Nebraska and North America
Ashlee Hartman and Matthew Bolek, Department
of Biology, University of Nebraska at Kearney,
Kearney, NE 68849 and Department of Zoology,
Oklahoma State University, Stillwater, OK, 74078
ABSTRACT
Collections Fresh fecal samples (1-4 hrs old)
were collected from individual untreated dogs.
Dog location, sex and age was recorded for each
animal and all samples were stored on ice or in
the refrigerator in individual Ziplock plastic
bags before processing. Dogs less then 1 year
old were classified as puppies, whereas dogs 1
year or older were classified as adults. Fecal
Processing and Parasite Identification Approximat
ely 5 g of feces from each dog along with 20 ml
Sheathers sugar solution (specific gravity 1.30)
was placed in individual Dixie cups, and mixed
thoroughly with an applicator stick. Samples
were strained through cheesecloth into 15 ml test
tubes and centrifuged at 1,500 rpm for 10 min.
Slides were scanned on a compound microscope at
100x magnification for protozoan cysts and
helminth eggs and larvae. All slides were
scanned three times to minimize the possibility
of missing low infections. Data
Analysis Overall and individual parasite
prevalence and mean species richness was
calculated for location, age and sex of dogs from
Nebraska, whereas overall prevalence and species
richness was calculated from the published
literature for different locations in North
America. The chi-square test for independence
was calculated to compare differences in overall
and individual parasite prevalence among
different locations, and age and sex of dogs.
Because variances were heteroscedastic, the
KruskalWallis test and the KolmogorovSmirnov
2-sample test were used to compare differences in
parasite species richness among different
locations in Nebraska and North America.
Most parasites use multiple hosts throughout
their life cycle and the conditions outside of
their internal environment must be adequate for
their survival and development. We examined dog
fecal samples from four animal shelters in
different areas of Nebraska that differ in their
average annual precipitation to evaluate the
effects of precipitation on parasite recruitment.
We found six species of protozoan and helminth
parasites infecting sheltered dogs from Nebraska
including Cystoisospora canis, Toxocara canis,
Toxocara leonine, Trichuris vulpis, Ancylostoma
caninum, and Taenia type eggs. We did not find
any statistically significant difference in
individual and overall parasite prevalence or
species richness among dogs sampled from
different locations in the state. However we did
find a statistically significant difference in
overall parasite prevalence and parasite species
richness when comparing our data to other
locations across the United States. Both overall
parasite prevalence and species richness
increased from west to east with average annual
precipitation across the United States. Our data
suggests that either the precipitation gradient
in Nebraska is not large enough to effect
parasite development in the external environment
or other factors may be important in effecting
parasite development in the external environment.
Companion animals such as dogs are important
reservoirs of a number of human zoonotic
protozoan and helminth parasites. However,
environmental conditions such as precipitation,
soil moisture and temperature directly influence
free living life cycle stages of different types
of parasites. Nebraska is an ideal location to
study parasitism throughout different environment
conditions across the state. Average yearly
precipitation varies from 28-34 inches in the
eastern part of the state, to 20-24 inches in the
central part of the state, and 16-18 inches in
the western part of the state. In this study we
document the first survey of intestinal parasites
of sheltered dogs in the state of Nebraska, and
examine the role of precipitation, dog age and
sex on the distribution of intestinal protozoan
and helminth parasites of dogs in Nebraska.
Additionally, we compare our data to similar
studies in other locations in North America that
vary in precipitation.
INTRODUCTION
RESULTS Of the 57 dogs examined, 11 (19.3)
were infected with six intestinal parasites
including 1 coccidian, 4 nematodes, and 1
tapeworm species (Fig 2). Individual parasite
species prevalence was low ranging from 0-17
(Table I). The overall mean species richness was
0.21 0.45. Forty six dogs had 0 parasite
species, 10 dogs had 1 parasite species and 1 dog
had 2 parasites species. There were no
statistically significant differences in overall
or individual parasite prevalence or species
richness among different locations, or age and
sex of dogs from Nebraska (P gt 0.05). However,
statistically significant differences were
observed in overall prevalence and mean parasite
species richness among intestinal protozoan and
helminth parasites from dogs examined from New
Mexico, Nebraska, Wisconsin and New Jersey (?2
236.71 P lt 0.0001 H corrected 269.569 P lt
0.0001 Fig. 3).
?2 236.71 P lt 0.0001
MATERIAL AND METHODS
Study Design During March-July 2008 we
examination fecal samples of sheltered dogs from
different locations in Nebraska. Animal shelters
were chosen based on distinct precipitation zones
in the state. The shelters that were chosen
were 1) North Platte Animal Shelter (Lincoln
Co.) 2) Kearney Area Humane Society (Buffalo
Co.) 3) Capital Humane Society in Lincoln
(Lancaster Co.) and 4) Beatrice Humane Society
(Gage Co) (Fig. 1). Additionally, our data was
compared to similar studies in 3 different
locations in North America that differ in their
average yearly precipitation to each other and
Nebraska (Fig 1) These location included 1) New
Mexico 3) Wisconsin and 4) New Jersey (Fig. 1).
Table I. Prevalence (No. infected/No. examined)
of intestinal parasites in shelter dogs from four
locations in Nebraska.
H corrected 269.569 P lt 0.0001
c
b
a
a
FIGURE 3. (A) Overall prevalence (given as ) of
intestinal protozoan and helminths parasites from
dogs in the United States surveyed by flotation
technique. (B) Mean species richness 1SD of
intestinal protozoan and helminth parasites from
dogs in the United States surveyed by flotation
techniques. The states represented are New
Mexico, Nebraska, Wisconsin, and New Jersey (from
left to right). Kolmogorov-Smirnov 2-sample
test a from b, P lt 0.05 a from c, and b from c,
all P lt 0.0001.
ACKNOWLEDGMENTS We would like to thank members of
the Kearney Area Humane Society, North Platte
Animal Shelter, Capital Humane Society, and
Beatrice Humane Society for their efforts to help
collect specimens. Without their cooperation,
this project would not have been possible. We
would also like to thank the Department of
Biology at UNK for use of facilities. Last, we
would like to thank Heather Tracy for helping us
obtain samples from North Platte Animal Shelter.
FIGURE 1. Precipitation maps of Nebraska and
North America and location of shelters where
fecal samples were obtained. (A) 1) North
Platte, Lincoln Co., 2) Kearney Buffalo C., 3)
Lincoln, Lancaster Co., and 4) Beatrice, Gage
Co. (B) 1) New Mexico, 2) Nebraska (pooled data),
3) Wisconsin, and 4) New Jersey. Maps from
USDA-NRCS National Water and Climate Center